An interesting addendum to your question: this is not a exclusively US based phenomenon. In Germany there are the Reichsbürgers they have similar ideas.

They think legally the state has no claim to rule and most people just don’t know they still live in the German Reich still.

So they have their own king selling them passports and they have pretty aggressive group think to try and enforce their claims.

My wife’s dad is one of them. The main thing I recognize comes from a pathological need to know better than everybody else. It’s very tightly coupled to their sense of worth and identity. They are better than everybody else because they have seen the light.

Pretty culty behavior and just enough pseudo truth to keep simple minds saying “yeah there might be something there”. Like “vaccination causes autism, they just don’t want you to know”.

Makes a loser in societies eyes, but a superhuman in their eyes. And yes, they still run into a wall and just keep trying to adjust their angle to hit that sacred sweet spot. Because now they need to prove how they are better and as they already have sacrificed so much they can’t be wrong to continue. (Just like a gambler who already lost a lot.)

So it’s a few psychological dynamics that grip into each other like gears and that ratchet them ever so tightly to their belief until there is no turning back.